(a) Field of the Invention
The present invention relates to a semiconductor device having a pixel protective circuit and, more particularly, to the structure of an address scanning circuit for an array of pixels provided in a semiconductor device.
(b) Description of the Related Art
In a semiconductor device having an X-Y address scanning circuit for a two-dimensional array of pixels, a horizontal shift register and a vertical shift register provided in the semiconductor device feed pixel selecting pulses in sequence. The shift registers consecutively turn on the horizontal switches and vertical switches to read pixel data one by one. The horizontal and vertical shift registers receive clock signals and data signals through respective signal lines for controlling the X-Y address to generate the pixel selecting pulses, as described in Patent Publication No. JP-A-8(1996)-105794.
In a conventional semiconductor device having an X-Y address scanning circuit, if a failure such as a signal stop occurs in a clock signal or data signal, the X-Y scanning circuit may stop the operation thereof or involve a malfunction, which sometime selects a single pixel for a long time. Such a long time selection of a single pixel imposes an overload on the selected pixel to deteriorate or destroy the selected pixel in the semiconductor device. Among the semiconductor devices having an X-Y scanning circuit, an infrared ray sensor is exemplified hereinafter wherein a bolometer is provided for each of pixels for photo-electric conversion.
If a disconnection occurs, for example, in a signal transmission line for controlling the X-Y address of the clock signal or data signal to thereby stop the X-Y scanning circuit or cause a malfunction in the horizontal shift register or vertical shift register, the bolometer of the selected pixel is subjected to overtime current flowing therethrough to be overheated by self heating, which causes characteristic deterioration or burnout destruction of the bolometer. Such a situation is similar in any semiconductor device having an address scanning circuit for an array of pixels.